NAME

sys/socket.h - Internet Protocol family

SYNOPSIS

#include <sys/socket.h>

DESCRIPTION

<sys/socket.h> makes available a type, socklen_t, which is an unsigned opaque integral type of length of at least 32 bits. To forestall portability problems, it is recommended that applications should not use values larger than 2³² - 1.

The <sys/socket.h> header defines the unsigned integral type sa_family_t.

The <sys/socket.h> header defines the sockaddr structure that includes at least the following members:

sa_family_t   sa_family       address family
char          sa_data[]       socket address (variable-length data)

The <sys/socket.h> header defines the msghdr structure that includes at least the following members:

void         *msg_name        optional address
socklen_t     msg_namelen     size of address
struct iovec *msg_iov         scatter/gather array
int           msg_iovlen      members in msg_iov
void         *msg_control     ancillary data, see below
socklen_t     msg_controllen  ancillary data buffer len
int           msg_flags       flags on received message

The <sys/socket.h> header defines the cmsghdr structure that includes at least the following members:

socklen_t     cmsg_len        data byte count, including the cmsghdr
int           cmsg_level      originating protocol
int           cmsg_type       protocol-specific type

Ancillary data consists of a sequence of pairs, each consisting of a cmsghdr structure followed by a data array. The data array contains the ancillary data message, and the cmsghdr structure contains descriptive information that allows an application to correctly parse the data.

The values for cmsg_level will be legal values for the level argument to the getsockopt() and setsockopt() functions. The system documentation should specify the cmsg_type definitions for the supported protocols.

Ancillary data is also possible at the socket level. The <sys/socket.h> header defines the following macro for use as the cmsg_type value when cmsg_level is SOL_SOCKET:

SCM_RIGHTS

Indicates that the data array contains the access rights to be sent or received.

The <sys/socket.h> header defines the following macros to gain access to the data arrays in the ancillary data associated with a message header:

CMSG_DATA(cmsg)

If the argument is a pointer to a cmsghdr structure, this macro returns an unsigned character pointer to the data array associated with the cmsghdr structure.

CMSG_NXTHDR(mhdr,cmsg)

If the first argument is a pointer to a msghdr structure and the second argument is a pointer to a cmsghdr structure in the ancillary data, pointed to by the msg_control field of that msghdr structure, this macro returns a pointer to the next cmsghdr structure, or a null pointer if this structure is the last cmsghdr in the ancillary data.

CMSG_FIRSTHDR(mhdr)

If the argument is a pointer to a msghdr structure, this macro returns a pointer to the first cmsghdr structure in the ancillary data associated with this msghdr structure, or a null pointer if there is no ancillary data associated with the msghdr structure.

The <sys/socket.h> header defines the linger structure that includes at least the following members:

int         l_onoff          indicates whether linger option is enabled
int         l_linger         linger time, in seconds

The <sys/socket.h> header defines the following macros, with distinct integral values:

SOCK_DGRAM

Datagram socket

SOCK_STREAM

Byte-stream socket

SOCK_SEQPACKET

Sequenced-packet socket

The <sys/socket.h> header defines the following macro for use as the level argument of setsockopt() and getsockopt().

SOL_SOCKET

Options to be accessed at socket level, not protocol level.

The <sys/socket.h> header defines the following macros, with distinct integral values, for use as the option_name argument in getsockopt() or setsockopt() calls:

SO_ACCEPTCONN

Socket is accepting connections.

SO_BROADCAST

Transmission of broadcast messages is supported.

SO_DEBUG

Debugging information is being recorded.

SO_DONTROUTE

bypass normal routing

SO_ERROR

Socket error status.

SO_KEEPALIVE

Connections are kept alive with periodic messages.

SO_LINGER

Socket lingers on close.

SO_OOBINLINE

Out-of-band data is transmitted in line.

SO_RCVBUF

Receive buffer size.

SO_RCVLOWAT

receive "low water mark"

SO_RCVTIMEO

receive timeout

SO_REUSEADDR

Reuse of local addresses is supported.

SO_SNDBUF

Send buffer size.

SO_SNDLOWAT

send "low water mark"

SO_SNDTIMEO

send timeout

SO_TYPE

Socket type.

The <sys/socket.h> header defines the following macros, with distinct integral values, for use as the valid values for the msg_flags field in the msghdr structure, or the flags parameter in recvfrom(), recvmsg(), sendto() or sendmsg() calls:

MSG_CTRUNC

Control data truncated.

MSG_DONTROUTE

Send without using routing tables.

MSG_EOR

Terminates a record (if supported by the protocol).

MSG_OOB

Out-of-band data.

MSG_PEEK

Leave received data in queue.

MSG_TRUNC

Normal data truncated.

MSG_WAITALL

Wait for complete message.

The <sys/socket.h> header defines the following macros, with distinct integral values:

AF_UNIX

UNIX domain sockets

AF_UNSPEC

Unspecified

AF_INET

Internet domain sockets

The <sys/socket.h> header defines the following macros, with distinct integral values:

SHUT_RD

Disables further receive operations.

SHUT_WR

Disables further send operations.

SHUT_RDWR

Disables further send and receive operations.

The following are declared as functions, and may also be defined as macros:

int     accept(int socket, struct sockaddr *address,
             socklen_t *address_len);
int     bind(int socket, const struct sockaddr *address,
             socklen_t address_len);
int     connect(int socket, const struct sockaddr *address,
             socklen_t address_len);
int     getpeername(int socket, struct sockaddr *address,
             socklen_t *address_len);
int     getsockname(int socket, struct sockaddr *address,
             socklen_t *address_len);
int     getsockopt(int socket, int level, int option_name,
             void *option_value, socklen_t *option_len);
int     listen(int socket, int backlog);
ssize_t recv(int socket, void *buffer, size_t length, int flags);
ssize_t recvfrom(int socket, void *buffer, size_t length,
             int flags, struct sockaddr *address, socklen_t *address_len);
ssize_t recvmsg(int socket, struct msghdr *message, int flags);
ssize_t send(int socket, const void *message, size_t length, int flags);
ssize_t sendmsg(int socket, const struct msghdr *message, int flags);
ssize_t sendto(int socket, const void *message, size_t length, int flags,
             const struct sockaddr *dest_addr, socklen_t dest_len);
int     setsockopt(int socket, int level, int option_name,
             const void *option_value, socklen_t option_len);
int     shutdown(int socket, int how);
int     socket(int domain, int type, int protocol);
int     socketpair(int domain, int type, int protocol,
             int socket_vector[2]);

SEE ALSO

accept(), bind(), connect(), getpeername(), getsockname(), getsockopt(), listen(), recv(), recvfrom(), recvmsg(), send(), sendmsg(), sendto(), setsockopt(), shutdown(), socket(), socketpair().